1. Field of the Invention
The invention relates to a mobile crane with a releasable coupling connecting the substructure to the superstructure, the coupling including a rotatably mounted ring with external teeth for meshing with a drive pinion of a slewing gear to rotate the ring.
2. Description of the Related Art
In the case of mobile or vehicle-mounted cranes with a high lifting capacity, both the substructure and the superstructure with jib become so heavy that it is necessary for the superstructure with jib to be transported on a special transport vehicle, in particular a low loader. For this purpose, the superstructure mounted rotatably on the substructure must be releasable from the latter. One of the requirements in this case is that the coupling be designed so that the superstructure can be released from the substructure simply and quickly and can be attached again to the latter and coupled to it simply and quickly.
Such a coupling is known from U.S. Pat. No. 3,921,817. It includes a ring having external teeth and fixed to the substructure. Mounted rotatably on the inside of this fixed ring is a further ring which is provided, distributed over the circumference, with inwardly extending webs. Arranged on the superstructure are two segments mounted in an articulated manner, which are provided on the outside, distributed over the circumference, with outwardly extending webs, the gaps between these being somewhat larger than the width of the webs of the inner ring. After the superstructure has been put in place, the two segments are pressed onto the inner ring as a result of the actuation of two piston/cylinder units and are coupled to one another by relative rotation in the manner of a bayonet fastening. The driving pinion of the slewing gear is mounted on the superstructure and comes into engagement with the external toothing of the fixed ring when the superstructure is put in place. The connection between the two segments and the rotatable inner ring is made via a plurality of adjustable link blocks arranged over the circumference on the rotatable inner ring.
An improved coupling is disclosed in DE 29 508 567 U1. This coupling consists of a holding ring connected to the substructure and of an axial cylindrical annular extension of an externally toothed ring mounted rotatably on the superstructure. The holding ring is provided with radially inwardly directed and the annular extension with radially outwardly directed claw-like webs which are arranged so as to be distributed uniformly over the circumference. They at least partially cover a common annular space concentric to the axis of rotation and are at a distance from one another such that the webs of one part can be pushed in the axial direction through the web gaps of the other part into radial planes offset to one another. By the toothed ring being rotated, the webs of one part engage behind the webs of the other part in the manner of a bayonet fastening.
One disadvantage of the known constructions is that the forces capable of being transmitted by means of this coupling are limited.
The object of the invention is to provide a releasable coupling for a mobile crane, one coupling connecting the substructure to the superstructure and being capable of transmitting higher forces, in particular for large grid cranes.
According to the teaching of the invention, the complementary ring has, both on the inside and on the outside, radially directed recesses and webs of the same length. The ring provided with the external teeth is provided with complementary recesses and webs. Selectively, web and recess and also web and web or recess and recess may be located opposite one another. For production reasons, the last-mentioned variant is to be preferred. The proposed arrangement has the advantage that high forces can consequently be transmitted and no unilateral moments occur on the middle ring.
According to a further feature of the invention, the ring provided with the external teeth is designed as a multiple-row roller-type rotary connection. Preferably, the roller-type rotary connection consists of a one-part or two-part fixed ring and of two or three annular rotatable elements which are connected to one other via screws. For high force transmission, a five-row or six-row roller-type rotary connection has proved beneficial, preferably the fifth roller set being arranged on the outside and the sixth roller set on the inside of the fixed ring.
Preferably, the complementary one-part or two-part ring is fastened to the superstructure, the webs being directed toward the substructure. In terms of weight distribution, it has proved beneficial to fasten and mount the driving pinion, together with the slewing gear, on the substructure. Where very large diameters are concerned, the arrangement of two slewing gears located opposite one another is advantageous.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.